OSLO — In a stunning surprise, the Nobel Committee announced Friday that it had awarded its annual peace prize to President Obama “for his extraordinary efforts to strengthen international diplomacy and cooperation between peoples.”

“He has created a new international climate,” the committee said in its announcement. President Obama’s name had not figured in speculation about the likely winner until minutes before the prize was announced here.

Likely candidates had been seen here as including human rights activists in China and Afghanistan and political figures in Africa.

The committee said it wanted to enhance Mr. Obama’s diplomatic efforts. “We are awarding Obama for what he has done,” the committee said. “Many other people and leaders and nations have to respond in a positive way” to President Obama’s diplomacy.

The announcement noted the special importance the committee attached to President Obama’s vision of a world without nuclear weapons. “Obama has as president created a new climate in international politics. Multilateral diplomacy has regained a central position, with emphasis on the role that the United Nations and other international institutions can play,” the committee said.